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Mulling over DDoS

The Wikileaks fracas is escalating, with hacktivists on both sides of the divide working to take down sites that are seen to be on the wrong side of the issue. Personally, I do not have any political opinion on either the Wikileaks issue or the attacks. I leave that to less technical authors to write on. Personally, I just like mulling over the whole problem of DDoS attacks.

Any reader of this blog should be familiar with what a DDoS attack is. But to me, the problem of a DDoS attack is similar to that of an arms race – the side with the bigger gun or bullet wins. In the case of the initial attack, Wikileaks moved over to AWS and was able to hold off attacks for a while. This is because Amazon had bigger pipes and defenses than the attackers. However, the attacks have taken a turn and secondary sites such as credit cards and law-firms are being hit as well. It seems like certain parties are taking this opportunity to settle some beef.

But back to the whole problem with DDoS.

I’ve mulled over this with my former boss and some co-workers, for the purpose of a clandestine project that I was working on. The conclusion that I came to is that a DDoS is effective in its simplicity – the side with the bigger pipes win. The company that I used to work for, has one of the biggest pipes in Malaysia and we could take people down, single-handedly, if we wanted to.

However, there are strategies to mitigate a DDoS attack.

Bigger pipes
Wikileaks moving to Amazon was in effect, buying bigger pipes. This mitigated attacks for a while until they got booted off Amazon. If it is not possible to buy pipes from a single provider, it would make sense to buy pipes from multiple providers and distributing the site across the globe. This is what Wikileaks has now done – distribute its content over a list of hundreds of worldwide mirrors operated by volunteers.

Faster software
DDoS attacks exploit the fact that a computer is kept busy by servicing network packets (either at the application or networking layers). Obviously, the solution to this problem would be to have bigger machines – this means having faster processors, larger memories, lighter operating systems. Surprisingly, some people do not realise that the TCP/IP stack plays an integral role in these attacks and if the OS has a more efficient stack, it would be able to withstand more punishment. Not all web-servers are created equal and some are able to handle concurrency better.

IPv6
One method that is not often thought of, is moving infrastructure over to IPv6. Most of the internet still runs on IPv4 today. In fact, many network providers simply do not cater to IPv6 and simply drop the packets from their network. Therefore, moving a site over to IPv6-only could help mitigate DDoS attacks by limiting the available sources of attack. Compromised botnets would be less effective if most of their machines were still on IPv4 only.

Future clouds
What would have been interesting would be if the attackers had shifted to launching attacks from cloud service providers. In fact, this was one of the queries that I raised once, in a meeting with a local cloud provider – launching attacks from within the cloud provider itself. If the provider is not careful, attackers could buy network and computing resources in order to launch attacks within the cloud itself. This would be difficult to detect because most cloud providers put their metering on external traffic, not internal ones. Imagine the attackers buying EC2s to attack Wikileaks from the inside of Amazon infrastructure. The attack would only need to be bad enough to take down the Wikileaks machines, without compromising the rest of Amazon’s infrastructure. Therefore, it is important for cloud providers to think about isolating their internal machines from each other.

Of course, there are many more considerations that could fit this little blog, but these were just some thoughts that I felt like writing down.